From b49a8a9dbbf7cf86293577e08746c219bb7d0de2 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Tue, 22 Mar 2016 19:14:38 +0000
Subject: [PATCH] CodeGen: check return types match when emitting tail call to
 builtin.

We were just completely ignoring the types when determining whether we could
safely emit a libcall as a tail call. This is clearly wrong.

Theoretically, we could dig deeper looking for incidental matches (much like
the generic code in Analysis.cpp does), but it's probably not worth it for the
few libcalls that exist.

llvm-svn: 264084
---
 llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp |  7 +++--
 llvm/test/CodeGen/ARM/tail-call-builtin.ll    | 37 +++++++++++++++++++++++++++
 llvm/test/CodeGen/X86/atomic-non-integer.ll   |  2 +-
 3 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 llvm/test/CodeGen/ARM/tail-call-builtin.ll

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index e7ab36a..40a3bdd 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -2247,9 +2247,12 @@ SDValue SelectionDAGLegalize::ExpandLibCall(RTLIB::Libcall LC, SDNode *Node,
   SDValue InChain = DAG.getEntryNode();
 
   // isTailCall may be true since the callee does not reference caller stack
-  // frame. Check if it's in the right position.
+  // frame. Check if it's in the right position and that the return types match.
   SDValue TCChain = InChain;
-  bool isTailCall = TLI.isInTailCallPosition(DAG, Node, TCChain);
+  const Function *F = DAG.getMachineFunction().getFunction();
+  bool isTailCall =
+      TLI.isInTailCallPosition(DAG, Node, TCChain) &&
+      (RetTy == F->getReturnType() || F->getReturnType()->isVoidTy());
   if (isTailCall)
     InChain = TCChain;
 
diff --git a/llvm/test/CodeGen/ARM/tail-call-builtin.ll b/llvm/test/CodeGen/ARM/tail-call-builtin.ll
new file mode 100644
index 0000000..c829cc5
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/tail-call-builtin.ll
@@ -0,0 +1,37 @@
+; RUN: llc -mtriple=thumbv7-linux-gnueabihf %s -o - | FileCheck %s
+
+define i64 @test_mismatched_call(double %in) {
+; CHECK-LABEL: test_mismatched_call:
+; CHECK: bl floor
+; CHECK: vmov r0, r1, d0
+
+  %val = tail call double @floor(double %in)
+  %res = bitcast double %val to i64
+  ret i64 %res
+}
+
+define double @test_matched_call(double %in) {
+; CHECK-LABEL: test_matched_call:
+; CHECK: b floor
+
+  %val = tail call double @floor(double %in)
+  ret double %val
+}
+
+define void @test_irrelevant_call(double %in) {
+; CHECK-LABEL: test_irrelevant_call:
+; CHECK-NOT: bl floor
+
+  %val = tail call double @floor(double %in)
+  ret void
+}
+
+define arm_aapcscc double @test_callingconv(double %in) {
+; CHECK: test_callingconv:
+; CHECK: bl floor
+
+  %val = tail call double @floor(double %in)
+  ret double %val
+}
+
+declare double @floor(double) nounwind readonly
diff --git a/llvm/test/CodeGen/X86/atomic-non-integer.ll b/llvm/test/CodeGen/X86/atomic-non-integer.ll
index 98fcd96..17b73ec 100644
--- a/llvm/test/CodeGen/X86/atomic-non-integer.ll
+++ b/llvm/test/CodeGen/X86/atomic-non-integer.ll
@@ -43,7 +43,7 @@ define half @load_half(half* %fptr) {
 ; CHECK-LABEL: @load_half
 ; CHECK: movw	(%rdi), %ax
 ; CHECK: movzwl	%ax, %edi
-; CHECK: jmp	__gnu_h2f_ieee
+; CHECK: callq	__gnu_h2f_ieee
   %v = load atomic half, half* %fptr unordered, align 2
   ret half %v
 }
-- 
2.7.4